Composite sintering materials using carbon nanotube and manufacturing method thereof

ABSTRACT

The present invention relates to a composite sintering materials using a carbon nanotube (including carbide nano particles, hereinafter the same) and a manufacturing method thereof, the method comprises the steps of: combining or generating carbon 5 nanotubes in metal powers, a compacted product, or a sintered product; growing and alloying the carbon nanotubes by compacting or sintering the metal powers, the compacted product, or the sintered product; and strengthening the mechanical characteristics by repeatedly performing the sintering process and the combining process or the generating process of the carbon nanotubes. The composite sintering materials using carbon nanotubes of the present invention have excellent mechanical, thermal, and electric and electronic characteristics as well as have effects of material cost reduction and manufacturing cost reduction due to reduced sintering temperature so that they are useful as materials for automotive parts, electric and electronic parts, space and aircraft parts, and molding and cutting tools, all of which include the composite sintering materials using carbon nanotubes.

TECHNICAL FIELD

The present invention relates to a composite sintering materials using a carbon nanotube (including carbide nano particles, hereinafter the same) and a manufacturing method thereof. The present invention is characterized by strengthening the mechanical characteristics of composite sintering materials by repeatedly performing processes of combining the carbon nanotubes with metal powders or generating the carbon nanotubes in the metal powders, impregnating and combining the carbon nanotubes in the pores of a compacted product or generating the carbon nanotubes in the pores, or impregnating and combining the carbon nanotubes in the pores of a sintered product or growing and alloying carbon nanotubes after generating the carbon nanotubes in the pores.

BACKGROUND ART

Composite sintering materials using a carbon nanotube of the present invention are completed by uniformly dispersing and combining the carbon nanotubes in metal powder particles, a compacted product, or a sintered product or generating the carbon nanotubes therein, and growing and alloying the carbon nanotubes, and then sintering them to have excellent mechanical, thermal, and electric and electronic characteristics as well as to have effects of material cost reduction and manufacturing cost reduction due to towered sintering temperature so that they are useful as materials for automotive parts, electric and electronic parts, space and aircraft parts, and molding and cutting tools, all of which include the composite sintering materials.

A representative carbon nanotube (CNT) among nanotubes has very excellent mechanical, thermal, and electrical characteristics and it is very thermally and chemically stable so that it can be applied as high elastic, high strength, and conductive composite material. Therefore, the carbon nanotube has been spotlighted as a new material usable in various fields such as polymer, ceramic composite material, etc., and it is a material that many studies have been made.

Since the carbon nanotube (CNT) known up to now has strong aggregation and high chemical stability, it is difficult to uniformly disperse it in a composite material matrix so that it is difficult to obtain carbon nano composite materials, making it impossible to effectively use the carbon nanotube (CNT).

As a result, various studies have recently been progressed in order to reveal the excellent characteristics of the carbon nanotube (CNT) using strong adhesive force with the matrix through the dispersion of the carbon nanotube (CNT) and a chemical processing.

Meanwhile, as a manufacturing method of metal composite materials, there has been proposed a casting method that infiltrates and disperses magnesium vapor in a porous molded product which is made of oxide based ceramics and at the same time, introduces nitrogen gas therein so as to infiltrate molten metal in the porous molded product, and a method of infiltrating metal materials as molten metal into carbon based materials which is dispersed with carbon materials using elastomer based on a pressing or non-pressing infiltration method. However, these methods are not sufficient in mechanical, thermal, electric and electronic characteristics.

TECHNICAL PROBLEM

It is an object of the present invention, to solve the above problems, to provide composite sintering materials and a manufacturing method thereof having excellent mechanical, thermal, and electric and electronic characteristics as well as having material cost reduction and manufacturing cost reduction due to lowered sintering temperature, so that they are useful as materials for automotive parts, electric and electronic parts, space and aircraft parts, and molding and cutting tools, all of which include the composite sintering materials

TECHNICAL SOLUTION

In order to accomplish the objects, a first aspect of the present invention comprises the steps of: manufacturing master alloys by combining carbon nanotubes with metal powders; growing or alloying the carbon nanotubes by compacting and then sintering the master alloy; generating the carbon nanotubes in the pores of a sintered product or impregnating and combining the carbon nanotubes therein; and strengthening mechanical characteristics by repeatedly performing the sintering process and the generating process of the carbon nanotubes in the sintered product or the impregnating and combining processes of the carbon nanotubes.

A second aspect of the present invention comprises the steps of: generating carbon nanotubes in metal powders; growing or alloying the carbon nanotubes by compacting and then sintering the metal powders in which the carbon nanotubes are generated; generating the carbon nanotubes in the pores of a sintered product or impregnating and combining the carbon nanotubes therein; and strengthening mechanical characteristics by repeatedly performing the sintering process and the generating process of the carbon nanotubes in the sintered product or the impregnating and combining processes of the carbon nanotubes.

A third aspect of the present invention comprises the steps of: generating carbon nanotubes in the pores of a compacted product after compacting metal powders or impregnating the carbon nanotubes therein to combine the metal powders with the carbon nanotubes in the pores of the compacted product; growing or alloying the carbon nanotubes by sintering the compacted product in which the carbon nanotubes are generated or with which the carbon nanotubes are combined; generating the carbon nanotubes in the pores of a sintered product or impregnating and combining the carbon nanotubes therein; and strengthening mechanical characteristics by repeatedly performing the sintering process and the generating process of the carbon nanotubes in the sintered product or the impregnating and combining processes of the carbon nanotubes.

A fourth aspect of the present invention comprises the steps of: generating carbon nanotubes in the pores of a finished product which is sintered after compacting metal powders or impregnating the carbon nanotubes therein to combine the metal powders with the carbon nanotubes in the pores of a sintered product; growing or alloying the carbon nanotubes by resintering the sintered product in which the carbon nanotubes are generated or with which the carbon nanotubes are combined; generating the carbon nanotubes in the pores of the sintered product or impregnating and combining the carbon nanotubes therein; and strengthening mechanical characteristics by repeatedly performing the sintering process and the generating process of the carbon nanotubes in the sintered product or the impregnating and combining processes of the carbon nanotubes.

A fifth aspect of the present invention comprises the steps of: manufacturing master alloys by combining carbon nanotubes with metal powders or generating the carbon nanotubes in metal powders; mixing the master alloy or the metal powders, wherein the carbon nanotubes are generated, with another metal powders or ceramic materials; growing or alloying the carbon nanotubes by compacting and then sintering the mixture; impregnating and combining the carbon nanotubes in the pores of a sintered product or generating the carbon nanotubes therein; and strengthening mechanical characteristics by repeatedly performing the sintering process and the generating process of the carbon nanotubes in the sintered product or the impregnating and combining processes of the carbon nanotubes.

A sixth aspect of the present invention comprises the steps of: mixing metal powders with ceramic materials; compacting the mixture or compacting and then sintering it; impregnating and combining the carbon nanotubes in the pores of a compacted product or a sintered product or generating the carbon nanotubes therein; growing or alloying the carbon nanotubes by sintering the molded product or the sintered product in which the carbon nanotubes are generated or with which the carbon nanotubes are combined; generating the carbon nanotubes in the pores of the sintered product or impregnating and combining the carbon nanotubes therein; and strengthening mechanical characteristics by repeatedly performing the sintering process and the generating process of the carbon nanotubes in the sintered product or the impregnating and combining processes of the carbon nanotubes.

A seventh invention of the present invention comprises the steps of: manufacturing master alloys by mixing and combining carbon nanotubes and metal powders or generating the carbon nanotubes in the metal powders; mixing the master alloy or the metal powders, wherein the carbon nanotubes are generated, with polymer materials; growing the carbon nanotubes by melting the mixture by a heater; injection-molding the mixed melting material; and aging the injection-molded product.

The composite sintering materials using the carbon nanotubes of the present invention has excellent mechanical, thermal, and electric and electronic characteristics by manufacturing master alloys by mixing the carbon nanotubes with the metal powder particles, impregnating and combining the carbon nanotubes in the compacted product or the sintered product, or generating the carbon nanotubes in the metal powder particles, the compacted product, or the sintered product; interposing the carbon nanotubes suffering from the compacting process or the sintering process under proper conditions in the metal powder particles, the compacted product, or the sintered product; and then combining, growing, and alloying the carbon nanotubes.

In the step of manufacturing the master alloys by mixing and combining the carbon nanotubes with the metal powder particles or the step of impregnating and combining the carbon nanotubes in the compacted product or the sintered product, it is preferable to use the carbon nanotubes in the dispersed state through the physical and chemical processes, and in the step of generating the carbon nanotubes in the metal powder particles, the compacted product, or the sintered product, it is preferable to chemically process the metal powder particles, the compacted product, or the sintered product and then process them by injecting liquid or gas having carbon group. Also, in the step of generating the carbon nanotubes, it is preferable to use acidic solution such as natal, phosphoric acid, sulfuric acid, HF solution, etc. and liquid or gas having carbon group such as ammonia, carbonic acid gas, carbonated water, methane gas, methanol, acetylene, benzene, glucose, sugar etc.

The metal powder particles in the step of combining the carbon nanotubes or the matrix ingredients of the compacted product and the sintered product in the step of impregnating the carbon nanotubes are preferably Fe, Ni, Co, W, and Si, but may also be alloy powders in which Fe, Ni, Co, W, and Si are alloyed. As other metal powders of the alloy powders, metal powders (Mo, Th, Ti, etc.) with high melting point or metal powders with low melting point (Al, Cu, Bi, Pb, Cd, Zn, Ce, Cs, K, Na, etc.) may be used.

Also, the metal powder particles in the step of generating the carbon nanotubes or the matrix ingredients of the molded product and the sintered product is preferably Fe, Ni, Co, W, and Si, but may also be alloy powders in which Fe, Ni, Co, W, and Si are alloyed. As other metal powders of the alloy powders, metal powders (Mo, Th, Ti, etc.) with high melting point or metal powders with low melting point (Al, Cu, Bi, Pb, Cd, Zn, Ce, Cs, K, Na, etc.) may be used.

In the step of manufacturing the master alloys in the present invention, it is preferable that the master alloys are manufactured by drying it at a temperature of up to 300° C. under an inert gas atmosphere or by directly growing the carbonano particles into the carbon nanotubes in the metal powder particles, in the step of generating the carbon nanotubes in the metal powders, the molded product, or the sintered product, it is preferable to generate the carbon nanotubes at a temperature of up to 1200° C. under an inert gas atmosphere, in the step of impregnating the carbon nanotubes in the compacted product or the sintered product, it is preferable to impregnate the carbon nanotubes using an impregnating machine at a temperature of up to 200° C., in the step of growing the carbon nanotubes, it is preferable to grow the carbon nanotubes at a temperature of up to 800° C. under an inert gas atmosphere, and in the step of alloying the carbon nanotubes, it is preferable to alloy the carbon nanotubes at a temperature of at least 900° C. under an inert gas atmosphere.

DESCRIPTION OF DRAWINGS

The above and other objects, features and advantages of the present invention will become apparent from the following description of preferred embodiments given in conjunction with the accompanying drawings, in which:

FIG. 1 is an electron microscope photograph (200 magnifications) at a sintering temperature of 400° C. of specimen (density of 6.2 g/cm³) obtained from an embodiment 1 of the present invention;

FIG. 2 is an electron microscope photograph (200 magnifications) at a sintering temperature of 500° C. of specimen (density of 6.2 g/cm³) obtained from an embodiment 1 of the present invention;

FIG. 3 is an electron microscope photograph (400 magnifications) at a sintering temperature of 400° C. of specimen (density of 6.2 g/cm³) obtained from an embodiment 1 of the present invention;

FIG. 4 is a scanning electron microscope photograph (SEM) (500 magnifications) at a sintering temperature of 400° C. of specimen (density of 6.2 g/cm³) obtained from an embodiment 1 of the present invention;

FIG. 5 is a scanning electron microscope photograph (10000 magnifications) at a sintering temperature of 300° C. of specimen (density of 6.2 g/cm³) obtained from an embodiment 1 of the present invention;

FIG. 6 is a scanning electron microscope photograph (10000 magnifications) at a sintering temperature of 500° C. of specimen (density of 6.2 g/cm³) obtained from an embodiment 1 of the present invention;

FIG. 7 is a scanning electron microscope photograph (500 magnifications) at a sintering temperature of 500° C. of specimen (density of 6.2 g/cm³) obtained from an embodiment 1 of the present invention;

FIG. 8 is a magnified view of the combining sites of FIG. 7;

FIG. 9 is a scanning electron microscope photograph (a: 5000 magnifications/b: 25000 magnifications) at a sintering temperature of 750° C. of AHC100.29 powder specimen (density of 6.8 g/cm³) obtained from an embodiment 1 of the present invention;

FIG. 10 is a scanning electron microscope photograph (a: 2000 magnifications/b: 5000 magnifications) at a sintering temperature of 900° C. of AHC100.29 powder specimen (density of 6.8 g/cm³) obtained from an embodiment 1 of the present invention;

FIG. 11 is a scanning electron microscope photograph (a: 2500 magnifications/b: 25000 magnifications) at a sintering temperature of 1000° C. of AHC100.29 powder specimen (density of 6.8 g/cm³) obtained from an embodiment 1 of the present invention;

FIG. 12 is a scanning electron microscope photograph (a: 1500 magnifications/b: 20000 magnifications) at a sintering temperature of 1100° C. of AHC100.29 powder specimen (density of 6.8 g/cm³) obtained from an embodiment 1 of the present invention;

FIG. 13 is a scanning electron microscope photograph (a: 2000 magnifications/b: 35000 magnifications) at a sintering temperature of 1000° C. of ABC100.30 powder specimen (density of 6.8 g/cm³) obtained from an embodiment 1 of the present invention;

FIG. 14 is a scanning electron microscope photograph (a: 5000 magnifications/b: 20000 magnifications) at a sintering temperature of 1000° C. of DAB powder specimen (density of 6.8 g/cm³) obtained from an embodiment 1 of the present invention;

FIG. 15 is a scanning electron microscope photograph (a: 2500 magnifications/b: 15000 magnifications) at a sintering temperature of 1000° C. of DAE powder specimen (density of 6.8 g/cm³) obtained from an embodiment 1 of the present invention;

FIG. 16 is a scanning electron microscope photograph (a: 5000 magnifications/b: 20000 magnifications) at a sintering temperature of 1000° C. of KAP powder specimen (density of 6.8 g/cm³) obtained from an embodiment 1 of the present invention;

FIG. 17 is a Bending photograph of toughness added specimens (density of 6.8 g/cm³) after being sintered at 1000° C., which are obtained from an embodiment 2 of the present invention;

FIG. 18 is a scanning electron microscope photograph (50 magnifications) of a fracture surface which is fractured after sintering PASC60 powder specimen (density of 6.8 g/cm³), at a sintering temperature of 1000° C., which is obtained from an embodiment 2 of the present invention;

FIG. 19 is a scanning electron microscope photograph (a: 5000 magnifications/b: 20000 magnifications) of toughness added specimen after sintering DAE powder specimen (density of 6.8 g/cm³) at 1000° C., which is obtained from an embodiment 2 of the present invention;

FIG. 20 is a scanning electron microscope photograph (a: 5000 magnifications/b: 20000 magnifications) of toughness added specimen after sintering PASC60 powder specimen (density of 6.8 g/cm³) at 1000° C., which is obtained from an embodiment 2 of the present invention;

FIG. 21 is a scanning electron microscope photograph (1000 magnifications) of toughness added specimen after sintering AHC100.29 powder specimen (density of 6.8 g/cm³) at 1000° C., which is obtained from an embodiment 2 of the present invention;

FIG. 22 is a scanning electron microscope photograph (1000 magnifications) of toughness added specimen after sintering ABC100.30 powder specimen (density of 6.8 g/cm³) at 1000° C., which is obtained from an embodiment 2 of the present invention;

FIG. 23 is a scanning electron microscope photograph (1000 magnifications) of toughness added specimen after sintering DAB powder specimen (density of 6.8 g/cm³) at 1000° C., which is obtained from an embodiment 2 of the present invention;

FIG. 24 is a scanning electron microscope photograph (1000 magnifications) of toughness added specimen after sintering DAE powder specimen (density of 6.8 g/cm³) at 1000° C., which is obtained from an embodiment 2 of the present invention;

FIG. 25 is a scanning electron microscope photograph (1000 magnifications) of toughness added specimen after sintering PASC60 powder specimen (density of 6.8 g/cm³) at 1000° C., which is obtained from an embodiment 2 of the present invention;

FIG. 26 is a scanning electron microscope photograph (1000 magnifications) of toughness added specimen after sintering KAP powder specimen (density of 6.8 g/cm³) at 1000° C., which is obtained from an embodiment 2 of the present invention;

FIG. 27 is a scanning electron microscope photograph (1000 magnifications) of toughness added specimen after sintering pure copper powder specimen (density of 6.8 g/cm³) at 1000° C., which is obtained from an embodiment 2 of the present invention;

FIG. 28 is a scanning electron microscope photograph (25000 magnifications) of toughness added specimen after resintering DAE powder specimen (density of 6.8 g/cm³) at 1100° C., which is obtained from an embodiment 3 of the present invention;

FIG. 29 is a scanning electron microscope photograph (15000 magnifications) of specimen sintering specimen (density of 6.8 g/cm³) generating carbon nanotubes in PASC60 powder at a sintering temperature of 600° C., which is obtained from an embodiment 4 of the present invention;

FIG. 30 is a scanning electron microscope photograph (a: 20000 magnifications/b: 50000 magnifications) of specimen sintering specimen (density of 6.8 g/cm³) generating carbon nanotubes in PASC60 powder molded product at a sintering temperature of 600° C., which is obtained from an embodiment 9 of the present invention;

FIG. 31 is a scanning electron microscope photograph (a: 5000 magnifications/b: 25 magnifications) of specimen sintering specimen (density of 6.8 g/cm³) generating carbon nanotubes in DAE powder molded product at a sintering temperature of 600° C., which is obtained from an embodiment 9 of the present invention;

FIG. 32 is a scanning electron microscope photograph (a: 5000 magnifications/b: 25000 magnifications) of specimen generating carbon nanotubes in PASC60 powder sintered product, which is obtained from an embodiment 14 of the present invention; and

FIG. 33 is a scanning electron microscope photograph (a: 5000 magnifications/b: 20000 magnifications) of specimen generating carbon nanotubes in DAE powder sintered product, which is obtained from an embodiment 14 of the present invention

BEST MODE

Hereinafter, the constitution of the present invention will be described in detail with reference to the embodiments.

Embodiment 1 (1) Manufacture of Sample

(a) Process of Manufacturing Master Alloy

The master alloy is manufactured by mixing and drying dispersed carbon nanotubes with AHC100.29 powder and ABC100.30 powder being used as a sintering alloy for an automotive structure, which are pure iron powder from Hoganas Co., DAB powder which is an alloy powder of iron, copper, nickel and molybdenum, DAE powder, PASC60 powder which is an alloy powder of iron and phosphorus, KAP powder which is an alloy powder of iron and tin, and pure copper powder.

The mixing method in the present embodiment 1 mixes the carbon nanotubes using a spraying non-gravity mixer to be able to uniformly distribute the dispersed carbon nanotubes, and the drying method performs a dry under an inert gas atmosphere. Also, in the used carbon nanotube, its average diameter is 20 nano, and length is 10 μm. The commercialized metal powder particle has a powder size of 50 μm to 250 μm.

The metal powders and the carbon nanotubes are mixed by means of a spray method so that in the mixing ratio of the metal powder to the carbon nanotube, the carbon nanotube is 0.1 wt % based on weight ratio.

(b) Compacting Process

The manufactured master alloy is compacted in a tensile specimen shape to allow AHC100.29 powder to have density of 6.2 g/cm³, 6.4 g/cm³, 6.6 g/cm³, 6.8 g/cm³ by being pressed by means of the press of 200 ton. And ASC 100.30, DAE, DAB, KAP and pure copper powder are pressed by means of the press of 200 ton to have density of 6.8 g/cm³.

The density measuring method measures the density after performing a sintering process according to KS D 0033 (method for determination of density of metal powder sintered materials).

(c) Sintering Process

Each of the manufactured three types of AHC100.29 specimens (density of 6.2 g/cm³, 6.4 g/cm³, 6.6 g/cm³) is sintered for one hour at a temperature of 100° C., 200° C., 300° C., 400° C., and 500° C. Also, the manufactured specimens (AHC100.29, ABC100.30, DAE, DAB, KAP, pure copper powder) at a density of 6.8 g/cm³ are sintered for one hour at a temperature of 750° C., 900° C., 1000° C., and 1100° C.

The sintering atmosphere is performed under nitrogen atmosphere and a Mesh Belt sintering furnace is used.

(2) Microstructure Analysis by Electron Microscope

As to three (6.2 g/cm³, 6.4 g/cm³, 6.6 g/cm³ in density as AHC100.29 power) of the specimens manufactured according to the process, the distribution situation, size of pores and the alloying degree of pure iron powder particles are examined by an electron microscope.

This measurement is performed by the electron microscope of 200 magnifications or 400 magnifications.

In order to take the electron microscope photograph, a wafer polishing is performed at final 1 μm powder, but only four types of 200° C., 300° C., 400° C., and 500° C. maintain mechanical strength capable of standing the polishing. However, the polishing cannot be performed on the specimen sintered at 100° C. since the particles are come off during the polishing.

FIG. 1 is an electron microscope photograph (200 magnifications) at a sintering temperature of 400° C. of specimen (density of 6.2 g/cm³) obtained from the embodiment 1 of the present invention, FIG. 2 is an electron microscope photograph (200 magnifications) at a sintering temperature of 500° C., and FIG. 3 is an electron microscope photograph (400 magnifications) at a sintering temperature of 400′.

As shown in FIGS. 1 to 3, in the specimen sintered at 400° C. the shape of powder particles is substantially maintained, but in the specimen sintered at 500° C. the sintered structure sintered at 1150° C., which is a sintering temperature of iron based powders in an existing powder metallurgy, is formed. Also, it can be found that fine alloy layers (combining sites of carbon nanotubes) are uniformly dispersed in each powder particle.

(3) Microstructure Analysis by Scanning Electron Microscope (SEM)

As to three (6.2 g/cm³, 6.4 g/cm³, 6.6 g/cm³ in density as AHC100.29 power) of the specimens manufactured according to the process, the distribution situation and size of carbon nanotubes, the growth of carbon nanotubes, the combining shape between the powder particles, and the carbon nanotube shape upon rupturing are examined by a scanning electron microscope (SEM).

This measurement is performed by the scanning electron microscope of 500 magnifications or 10000 magnifications.

FIG. 4 is a scanning electron microscope (SEM) photograph (500 magnifications) at a sintering temperature of 400° C. of specimen (density of 6.2 g/cm³) obtained from the embodiment 1 of the present invention, FIG. 5 is a scanning electron microscope (SEM) photograph (10000 magnifications) at a sintering temperature of 300° C., FIG. 6 is a scanning electron microscope photograph (10000 magnifications) at a sintering temperature of 500° C., FIG. 7 is a scanning electron microscope photograph (500 magnifications) at a sintering temperature of 500° C., and FIG. 8 is a magnified view of the combining sites of FIG. 7.

As shown in FIGS. 4 to 8, the carbon nanotubes are uniformly distributed over all the specimens. It can be found from FIGS. 4 to 8 that as the temperature is high, the growth speed of the carbon nanotubes is increased so that the carbon nanotubes are grown and many carbon nanotubes remain in a non-combined shape, at the temperature of 300° C. upon rupturing, however, at a temperature of 500° C., most of carbon nanotubes are combined to be ruptured upon cutting the specimens. Also, it can be found that the ends of the carbon nanotubes (or growth compounds) are alloyed with the powder particles to be combined and the ruptured shape of the growth compound has an orthorhombic shape of carbide (cementite, Fe3C). Also, the sintered combination between the powder particles around the combining sites is made.

Also, as to the specimens (AHC100.29, AHC100.30, DAE, DAB, KAP, pure copper power) manufactured at 6.8 g/cm³, the distribution shape of carbon nanotubes, the growth of carbon nanotubes, the alloying shape, and the carbon nanotube upon rupturing, at each sintering temperature (750° C., 900° C., 1000° C., and 1100° C.), are examined by the scanning electron microscope (SEM).

FIG. 9 is a scanning electron microscope (SEM) photograph (5000 magnifications and 25000 magnifications) at a sintering temperature of 750° C. of AHC100.29 powder specimen (density of 6.8 g/cm³) obtained from the embodiment 1 of the present invention, FIG. 10 is a scanning electron microscope (SEM) photograph (2000 magnifications and 5000 magnifications) at a sintering temperature of 900° C., FIG. 11 is a scanning electron microscope photograph (2500 magnifications and 25000 magnifications) at a sintering temperature of 1000° C., FIG. 12 is a scanning electron microscope photograph (1500 magnifications and 20000 magnifications) at a sintering temperature of 1100° C., FIG. 13 is a scanning electron microscope (SEM) photograph (2000 magnifications and 35000 magnifications) at a sintering temperature of 1000° C. of AHC100.30 powder specimen (density of 6.8 g/cm³), FIG. 14 is a scanning electron microscope (SEM) photograph (5000 magnifications and 20000 magnifications) at a sintering temperature of 1000° C. of DAB powder specimen (density of 6.8 g/cm³), FIG. 15 is a scanning electron microscope (SEM) photograph (2500 magnifications and 15000 magnifications) at a sintering temperature of 1000° C. of DAE powder specimen (density of 6.8 g/cm³), and FIG. 16 is a scanning electron microscope (SEM) photograph (5000 magnifications and 20000 magnifications) at a sintering temperature of 750° C. of KAP powder specimen (density of 6.8 g/cm³).

As shown in FIGS. 9 to 16, in the sintering temperature of 750° C. to 900° C., the shape of the small carbon nanotubes, which are uniformly dispersed, are disappeared and only the shape of the large carbon nanotubes remains. Also, considering the shape of large carbon nanotubes in the sintering temperature of 750° C. to 900° C., the shape of the nanotubes still remains. However, it can be found that in the sintering temperature of 1000° C. to 1100° C., the carbon nanotubes are changed into a shape where the large nanotubes get entangled in the small carbon nanotubes and are then changed into a shape covering the surfaces of the metal particles. And, the alloying is progressed in the portions where the carbon nanotubes are combined so that it can be found that as the sintering temperature is increased, the alloyed portions are widened. Therefore, if the master alloy powders uniformly dispersing and combining the carbon nanotubes in the powder particles are sintered, as the sintering temperature is raised, the alloying of the carbon nanotubes and the powder particles is progressed as well as the carbon nanotubes are combined and at the same time, grown, and when exceeding a particular temperature, the shape of the carbon nanotubes is broken, and then the carbon nanotubes then cover the surfaces of the powder particles and the alloying of the carbon nanotubes and the powder particles is continuously progressed. In the specimen that the master alloy powders dispersing and combining the carbon nanotubes in the KAP powders and the pure copper powders are sintered, it cannot be confirmed whether there are the carbon nanotubes.

(4) Mechanical Property Measurement by Hardness Test

The mechanical physical property values of the specimens manufactured according to the process are measured by means of a Vickers hardness tester.

The test method follows KS B 0811 (Method of Vickers hardness test). A test load of 98.1N (10 kg) is performed and a ten-point measurement is used. Each of two values from the top and bottom of the measured values is discarded so that the hardness is computed by performing an arithmetic mean using the remaining six points.

The Vickers hardness test results per the sintering temperature for the AHC100.29 powder specimen whose density is 6.2 g/cm³, 6.4 g/cm³, and 6.6 g/cm³ are indicated in Table 1.

As in the Table 1, although the sintering temperature is too low to measure the hardness values in the conventional powder metallurgy, the hardness values can be measured in 400° C. to 500° C. Also, as the density is increased, the hardness values per the sintering temperature become high.

The Vickers hardness test results per the sintering temperature for each powder (AHC100.29, ABC100.30, DAB, DAE, KAP, pure copper) specimen with density of 6.8 g/cm³ are indicated in the following Table 2.

As in the Table 2, the hardness values are very highly measured even in temperature (up to 1000° C.) lower than that of the conventional powder metallurgy (footnote 1). It can be found that the sintered product can be manufactured in temperature lower than that of the conventional powder metallurgy. However, the difference in the hardness values between two specimens sintered at 1000° C. and 1100° C., respectively, are different according to the powders. Accordingly, it can be found that there is the difference in the alloying temperature of the carbon nanotubes according to the powders.

TABLE 1 <The hardness measurement results according to the change in sintering temperature and density> Sintering temperature Density (g/cm³) Hardness (Hv = 10) 100° C. 6.2 — 6.4 — 6.6 — 200° C. 6.2 No measurement 6.4 No measurement 6.6 No measurement 300° C. 6.2 No measurement 6.4 No measurement 6.6 No measurement 400° C. 6.2 10 6.4 10 6.6 12 500° C. 6.2 16 6.4 17 6.6 22

TABLE 2 <The hardness measurement results according to the change in sintering temperature per power types> Powder name Sintering temperature Hardness (Hv = 10) AHC100.29 750° C. 70 900° C. 78 1000° C. 90 1100° C. 104 ABC100.30 750° C. 86 900° C. 101 1000° C. 120 1100° C. 121 DAB 750° C. 76 900° C. 85 1000° C. 112 1100° C. 127 DAE 750° C. 76 900° C. 85 1000° C. 100 1100° C. 122 PASC60 750° C. 82 900° C. 105 1000° C. 142 1100° C. 158 KAP 750° C. 68 Pure copper 750° C. 38 Footnote 1) in the case of the sintering alloy for the automotive structure, the Vickers hardness values are as follows. SMF 4020M is at least 60, SMF 4030M is at least 80, SMF 4040M is at least 100, and SMF 9060M is at least 200, based on the sintered finished product (approximately sintering temperature 1150° C.).

(5) Mechanical Property Measurement by Tensile Test

The tensile test for the respective powder (AHC100.29, ABC100.30, DAB, DAE, KAP, pure copper) specimens with density of 6.8 g/cm³ among the specimens manufactured according to the process is performed by means of a universal testing machine.

The test specimen follows JIS Z 2550 (sintered materials for structural parts) and the test method performs the tensile test according to KS B 0802 (method of tensile test for metallic materials).

The tensile test results are indicated in the following table 3.

In as the table 3, although there is a tensile strength even in temperature (up to 1000° C.) lower than that of the conventional powder metallurgy (footnote 2), the carbon nanotube content of 0.1% is not enough to intensify the strength.

TABLE 3 <The tensile strength measurement result according to the change in the sintering temperature per powder types> Powder name Sintering temperature Tensile strength (kgf/mm2) AHC100.29 750° C. 10.65 900° C. 12.45 1000° C. 14.14 1100° C. 14.32 ABC100.30 750° C. 7.33 900° C. 14.79 1000° C. 15.04 1100° C. 16.09 DAB 750° C. 4.98 900° C. 12.88 1000° C. 16.47 1100° C. 18.62 DAE 750° C. 6.64 900° C. 12.57 1000° C. 18.77 1100° C. 22.81 PASC60 750° C. 2.16 900° C. 8.03 1000° C. 22.87 1100° C. 27.63 KAP 750° C. 11.85 Pure copper 750° C. 1.06 Footnote 2) in the case of the sintering alloy for the automotive structure, the Vickers hardness values are as follows. SMF 4020M is at least 20, SMF 4030M is at least 30, SMF 4040M is at least 40, and SMF 9060M is at least 60, based on the sintered finished product (approximately sintering temperature 1150° C.).

Embodiment 2 (1) Manufacture of Sample

(a) Process of Manufacturing Master Alloy (the Same as the Embodiment 1)

(b) Compacting Process

The manufactured master alloy is compacted in a tensile specimen shape to allow AHC100.29, ASC 100.30, DAE, DAB, KAP, and pure copper powders to have density of 6.8 g/cm³ by being pressed by means of the press of 200 ton. The remaining processes are the same as the embodiment 1.

(c) Sintering Process

Each of the manufactured specimens is sintered for one hour at a temperature of 1000° C. and 1100° C. The remaining processes are the same as the embodiment 1.

(d) Process of Generating Carbon Nanotube (Toughness Adding Process)

After dipping the manufactured finished product into diluted HF solution, natal, diluted sulfuric acid or phosphoric acid, and ammonia at a proper temperature is injected and acetylene, methane gas, or carbonic acid gas is then injected to generate the carbon nanotubes so that the toughness is added.

(2) Microstructure Analysis by Scanning Electron Microscope (SEM)

As to the specimens manufactured according to the process, the distribution shape of carbon nanotubes, the combining shape between the powder particles, and the carbon nanotube shape upon rupturing are examined by a scanning electron microscope (SEM).

This measurement is performed by the scanning electron microscope (SEM) of 50 magnifications, 1000 magnifications, 5000 magnifications, or 20000 magnifications.

FIG. 17 is a Bending photograph of toughness added specimens after being sintered at 1000° C., which are obtained from the embodiment 2 of the present invention, FIG. 18 is a scanning electron microscope photograph (50 magnifications) of a fracture surface fractured after being sintered at a sintering temperature of 1000° C. and adding toughness, FIG. 19 is a scanning electron microscope photograph (5000 magnifications and 20000 magnifications) of toughness added DAE powder specimen after being sintered at 1000° C., FIG. 20 is a scanning electron microscope photograph (5000 magnifications and 20000 magnifications) of toughness added PASC60 powder specimen after being sintered at 1000° C., FIG. 21 is a scanning electron microscope photograph (1000 magnifications) of toughness added AHC100.30 powder specimen after being sintered at 1000° C., FIG. 22 is a scanning electron microscope photograph (1000 magnifications) of toughness added ABC100.30 powder specimen after being sintered at 1000° C., FIG. 23 is a scanning electron microscope photograph (1000 magnifications) of toughness added DAB powder specimen after being sintered at 1000° C., FIG. 24 is a scanning electron microscope photograph (1000 magnifications) of toughness added DAE powder specimen after being sintered at 1000° C., FIG. 25 is a scanning electron microscope photograph (1000 magnifications) of toughness added PASC60 powder specimen after being sintered at 1000° C., FIG. 26 is a scanning electron microscope photograph (1000 magnifications) of toughness added KAP powder specimen after being sintering at 1000° C., and FIG. 27 is a scanning electron microscope photograph (1000 magnifications) of toughness added pure copper powder specimen after being sintered at 1000° C.

As shown in FIGS. 17 to 27, it can be confirmed that the carbon nanotubes are generated and combined over all the specimens and are generated in a gauze form on the surfaces of the metal powders so that the ruptured sites are torn upon rupturing. Therefore, it is judged that the sintered product has toughness. However, it can not be judged whether there are the carbon nanotubes in the KAP powder specimen and the pure copper powder specimen. In order to strengthen mechanical, electric and electronic, and thermal characteristics using the carbon nanotubes in Cu or Cu alloy powders, it is judged that after the carbon nanotubes are generated in Fe or Ni master alloy powders or in Fe or Ni powder, they should mixed and sintered.

(3) Mechanical Property Measurement by Tensile Test (the Same as the Embodiment 1)

The tensile test results are indicated in the following table 4. As in the table 4, the tensile strength measurement results after suffering from the toughness adding process indicates that the change in tensile strength before/after adding the toughness is small, but the elongation is very increased.

TABLE 4 <The tensile strength and elongation measurement results according to the change in sintering temperature per powder types> Before adding toughness After adding toughness (kgf/mm 2) (kgf/mm 2) Tensile Tensile Powder Sintering strength Elongation strength Elongation name temperature (kgf/mm 2) (%) (kgf/mm 2) (%) AHC100.29 1000° C. 14.14 Less than 1 14.09 7.40 1100° C. 14.32 Less than 1 13.68 12.72 ABC100.30 1000° C. 15.04 Less than 1 19.64 10.04 1100° C. 16.09 Less than 1 16.16 14.52 DAB 1000° C. 16.47 Less than 1 19.88 11.04 1100° C. 18.62 Less than 1 21.93 12.20 DAE 1000° C. 18.77 Less than 1 23.61 9.88 1100° C. 22.81 Less than 1 25.64 10.84 PASC60 1000° C. 22.87 Less than 1 19.15 7.92 1100° C. 27.63 Less than 1 25.99 8.96 Footnote 3) in the case of the sintering alloy for the automotive structure, the elongation is as follows. SMF 4020M is at least 1.0%, SMF 4030M is at least 2.0%, SMF 4040M is at least 1.2%, and SMF 9060M is at least 1.5%, based on the sintered finished product (approximately sintering temperature 1150° C.).

As described above, the present invention generates and combines the carbon nanotubes in the metal powders adjacent to the pores which exists in the sintered product to increase the toughness, making it possible to obtain the composite sintering materials with more excellent mechanical characteristics than the conventional sintered materials with strong brittleness.

Embodiment 3 (1) Manufacture of Sample

(a) Process of Manufacturing Master Alloy (the Same as the Embodiment 1)

(b) Compacting Process

The manufactured master alloy is compacted in a tensile specimen shape to allow PASC60 and DAE powders to have density of 6.8 g/cm³ by being pressed by means of the press of 200 ton. The remaining processes are the same as the embodiment 1.

(c) Sintering Process

The manufactured specimens are sintered for one hour at a temperature of 1100° C. The remaining processes are the same as the embodiment 1.

(d) Process of Generating Carbon Nanotube (Toughness Adding Process) (the Same as the Embodiment 2)

(e) Resintering Process

The manufactured toughness added finished product is resintered for one hour at a temperature of 1100° C.

The sintering atmosphere is performed under nitrogen atmosphere and a Mesh Belt sintering furnace is used.

(2) Mechanical Property Measurement by Tensile Test (the Measurement Method is the Same as the Embodiment 1)

The tensile test results are indicated in the following table 5. As in the table 5, in the tensile strength and elongation measurement results after suffering from the resintering process at a temperature of 1100° C., the elongation is slightly changed as compared to the toughness added sintered product, but the tensile strength is very increased.

TABLE 5 <The tensile strength and elongation measurement results after performing the resintering at 1100° C.> Results of embodiment 2 Results of embodiment 3 Tensile Initial Tensile Powder strength Elongation sintering strength Elongation name (kgf/mm 2) (%) temperature (kgf/mm 2) (%) AHC100.29 13.68 12.72  900° C. 15.04 9.28 1000° C. 17.00 11.54 1100° C. 17.39 12.12 ABC100.30 16.16 14.52  900° C. 16.60 10.76 1000° C. 17.55 13.89 1100° C. 20.07 14.23 DAB 21.93 12.20  900° C. 34.34 9.97 1000° C. 35.23 11.10 1100° C. 35.71 11.98 DAE 25.64 10.84  900° C. 37.23 9.65 1000° C. 40.68 10.56 1100° C. 43.75 11.03 PASC60 25.99 8.96  900° C. 27.76 7.64 1000° C. 30.74 8.88 1100° C. 31.75 9.23

As described above, the present invention resinters, grows, and alloys the carbon nanotubes in the metal powders adjacent to the pores which exists in the sintered product to increase the strength and maintain the toughness, making it possible to obtain the composite sintering materials with more excellent mechanical characteristics with the intensified toughness and strength.

Embodiment 4 (1) Manufacture of Sample

(a) Process of Manufacturing Master Alloy (the Same as the Embodiment 1)

(b) Compacting Process (the Same as the Embodiment 1)

The manufactured master alloy is compacted in a tensile specimen shape to allow PASC60 and DAE powders to have density of 6.8 g/cm³ by being pressed by means of the press of 200 ton. The remaining processes are the same as the embodiment 1.

(c) Sintering Process

The manufactured specimens are sintered for one hour at a temperature of 1100° C. The remaining processes are the same as the embodiment 1.

(d) Process of Generating Carbon Nanotube (Toughness Adding Process) (the Same as the Embodiment 2)

(e) Resintering Process (the Same as the Embodiment 3)

(f) Retoughness Adding Process (the Same as the (d) Process of the Embodiment 2)

(2) Microstructure Analysis by Scanning Electron Microscope (SEM)

In the specimens manufactured by the process, the generation, growth, and alloying shape of the carbon nanotubes are examined by means of the scanning electron microscope (SEM).

FIG. 28 is a scanning electron microscope photograph (25000 magnifications) of retoughness added DAE powder specimen after being resintered at 1100° C., which is obtained from the embodiment 4 of the present invention.

As shown in FIG. 28, it can be found that the carbon nanotubes mixed in the metal powder particles and the carbon nanotubes generated in the step of adding the toughness are grown and alloyed, and the carbon nanotubes are regenerated by suffering from the retoughness adding step after being resintered. It can be found that the mechanical properties are further strengthened by the repetition of sintering-toughness adding-resintering-retoughness adding-resintering processes

Embodiment 5 (1) Manufacture of Sample

(a) Process of Generating Carbon Nanotube in Metal Powder Particle

The carbon nanotubes are generated in PASC60 powder by uniformly mixing the PASC60 powder used as the sintered alloy for the automotive structure, which is an alloy powder of iron and phosphorous from Hoganas Co., with diluted HF solution, natal, diluted sulfuric acid or phosphoric acid using a spraying non-gravity mixer, and injecting ammonia while applying heat at a proper temperature and then injecting acetylene, methane gas, or carbonic acid gas.

(b) Compacting Process

The manufactured master alloy is compacted in a tensile specimen shape to have density of 6.8 g/cm³ by being pressed by means of the press of 200 ton.

The density measuring method measures density after performing a sintering process according to KS D 0033 (method for determination of density of metal powder sintered materials).

The remaining processes are the same as the embodiment 1.

(c) Sintering Process

The manufactured specimen is sintered for one hour at a temperature of 600° C.

The sintering atmosphere is performed under nitrogen atmosphere and a Mesh Belt sintering furnace is used.

(2) Microstructure Analysis by Scanning Electron Microscope (SEM)

In the specimens manufactured by the process, the shape grown when the carbon nanotubes generated in the metal powder particles is sintered at a sintering temperature of 600° C. is examined by means of the scanning electron microscope (SEM).

FIG. 29 is a scanning electron microscope photograph (15000 magnifications) of specimen generating carbon nanotubes in the metal powder particles at a sintering temperature of 600° C., which is obtained from the embodiment 4 of the present invention;

As shown in FIG. 29, it can be found that the carbon nanotubes covers the metal powder particles by being generated along with the carbon particles in the metal powder particles, but unlike the master alloy powder uniformly dispersing and combining the carbon nanotubes, they are not grown as large carbon nanotubes even at a sintering temperature of 600° C.

Embodiment 6 (1) Manufacture of Sample

(a) Process of Generating Carbon Nanotube in Metal Powder Particle (the Same as the Embodiment 5)

(b) Compacting Process (the Same as the Embodiment 5)

(c) Sintering Process

The manufactured specimen is sintered for one hour at a temperature of 1100° C.

The sintering atmosphere is performed under nitrogen atmosphere and a Mesh Belt sintering furnace is used.

(2) Mechanical Property Measurement by Tensile Test (the Measuring Method is the Same as the Embodiment 1)

The tensile test results are indicated in the following table 6.

As in the table 6, it can be found that the tensile strength and elongation are more increased than the specimen of the embodiment 1 made by mixing and combining the carbon nanotubes of 0.1%. It is judged that it is difficult to quantitatively measure the amount of the carbon nanotubes generated in the metal powder particles, but the larger amount of the carbon nanotubes is formed than the case where the carbon nanotubes of 0.1% is mixed. Also, it is judged that in the carbon nanotubes mixed and combined in the metal powder particles, the shape of the tubes is broken when exceeding a particular sintering temperature so that it has a little effect on the mechanical physical property values such as the elongation, while the shape of the carbon nanotubes formed in the metal powder particles is maintained at a temperature of 1100° C. so that it maintains the elongation even after being sintered at a temperature of 1100° C. It can be found that as the amount of the carbon nanotubes dispersed and combined in the metal powder particles is increased, the tensile strength is increased. However, since it is difficult to make quantifiable the amount of the carbon nanotubes generated, it is necessary to establish the working conditions conforming to the mechanical values.

TABLE 6 <The tensile strength measurement results after performing the sintering at 1100° C.> Embodiment 1 Embodiment 6 Tensile Tensile Powder Sintering Strength Elongation strength Elongation name temperature (kgf/mm 2) (%) (kg/mm 2) (%) PASC60 1100° C. 27.63 Less than 1 39.40 8.67

Embodiment 7 (1) Manufacture of Sample

(a) Process of Generating Carbon Nanotube in Metal Powder Particle (the Same as the Embodiment 5)

(b) Compacting Process (the Same as the Embodiment 5)

(c) Sintering Process (the Same as the Embodiment 6)

(d) Process of Further Generating Carbon Nanotube (the Same as the Embodiment 2)

(e) Resintering Process

The manufactured toughness adding finished product is resintered for one hour at a temperature of 600° C. and 1100° C. The remaining processes are the same as the embodiment 3.

(2) Mechanical Physical Property Measurement by Tensile Test (the Measuring Method is the Same as the Embodiment 1)

The tensile test results are indicated in the following table 7.

As in the Table 7, in the tensile strength and elongation measurement results after suffering from the resintering process and the generating process of the carbon nanotubes, the difference in the tensile strength and elongation are not large as compared to the specimen sintered after generating the carbon nanotubes in the metal powder particles. Also, the difference in the tensile strength of the specimen resintered at 600° C. is not large, but the tensile strength of the specimen resintered at 1100° C. is increased by about 10%. It can be found that when further generating and sintering the carbon nanotubes in the sintered product obtained from the embodiment 6, they should be sintered at the sintering temperature performing the further alloying in order to increase the mechanical strength.

TABLE 7 <The tensile strength and elongation measurement results> Powder Results of embodiment 6 Results of embodiment 7 name Tensile Tensile Powder Sintering strength Elongation Resintering strength Elongation name temperature (kgf/mm 2) (%) temperature (kgf/mm 2) (%) PASC60 1100° C. 39.40 8.67  600° C. 40.28 13.87 PASC60 1100° C. 39.40 8.67 1100° C. 46.86 14.70

Embodiment 8 (1) Manufacture of Sample

(a) Compacting Process

PASC60 powder used as the sintered alloy for the automotive structure, which is an alloy powder of iron and phosphorous from Hoganas Co., and DAE powders are compacted in a tensile specimen shape to have density of 6.8 g/cm³ by being pressed by means of the press of 200 ton.

The density measuring method measures density after performing a sintering process according to KS D 0033 (method for determination of density of metal powder sintered materials).

(b) Process of Impregnating and Combining Carbon Nanotube in Compacted Product

In a manufactured compacted product, organic solution where carbon nanotubes are dispersed is impregnated in the pores of the molded product by using a vacuum impregnating machine and is heated at a proper temperature so that the carbon nanotubes are combined in the metal powder particles adjacent to the pores of the compacted product.

(c) Sintering Process

The manufactured specimen is sintered for one hour at a temperature of 1100° C.

The sintering atmosphere is performed under nitrogen atmosphere and a Mesh Belt sintering furnace is used.

(2) Mechanical Physical Property Measurement by Tensile Test (the Measurement Method is the Same as the Embodiment 1)

The tensile test results are indicated in the following table 8.

As in the Table 8, it can be found that the mechanical strength in the case where the carbon tubes are impregnated and sintered in the compacted product is weaker as compared to that in the case where the carbon nanotubes are mixed and sintered in metal powder particles. It is judged that since the carbon nanotubes are combined in the pores existing in the molded product to grow and alloy when the carbon tubes are impregnated in the compacted product, the disperse of the carbon nanotubes are more non-uniform and the amount of the carbon nanotubes is little to have a lower mechanical strength, as compare to the case where the carbon nanotubes are mixed and sintered in the metal powder particles.

TABLE 8 <The tensile strength measurement results after performing the sintering at 1100° C.> Powder name Tensile strength(kgf/mm2) Powder name Results of embodiment 6 Results of embodiment 7 PASC60 27.63 23.45 DAE 22.81 19.87

Embodiment 9 (1) Manufacture of Sample

(a) Compacting Process (the Same as the Embodiment 8)

(b) Process of Impregnating and Combining Carbon Nanotube in Compacted Product (the Same as the Embodiment 8)

(c) Sintering Process (the Same as the Embodiment 8)

(d) Process of Generating Carbon Nanotube (Toughness Adding Process)

After dipping the manufactured sintered and finished product into diluted HF solution, natal, diluted sulfuric acid or phosphoric acid, ammonia at a proper temperature is injected and acetylene, methane gas, or carbonic acid gas is then injected to generate the carbon nanotubes so that the toughness is added.

(e) Resintering Process (the Same as the Embodiment 3)

The manufactured toughness adding finished product is resintered for one hour at a temperature of 600° C. and 1100° C. The remaining processes are the same as the embodiment 3.

(2) Mechanical Physical Property Measurement by Tensile Test (the Measuring Method is the Same as the Embodiment 1)

The tensile test results are indicated in the following table 9.

As in the Table 9, it can be found that the tensile strength generating the carbon nanotubes in a specimen impregnating and sintering the carbon nanotubes in the compacted product obtained from the embodiment 8 and resintering them at a temperature of 600° C. is hardly changed as compared to the specimen obtained from the embodiment 8. However, the tensile strength of the specimen resintered at a temperature of 1000° C. is much more increased as compared to the specimen obtained from the embodiment 8. It can be found that the strength is increase only when the generated carbon nanotubes are resintered above the temperature that the alloy is made. Also, it can be found that although the elongation is different according to the resintering temperature, if the carbon nanotubes are generated, it is not greatly affected by the resintering temperature but has similar elongations.

TABLE 9 <The tensile strength and elongation measurement after adding toughness and resintering> Powder Results of embodiment 3 Results of embodiment 9 name Tensile Tensile Powder Sintering strength Elongation Resintering strength Elongation name temperature (kgf/mm 2) (%) temperature (kgf/mm 2) (%) PASC60 1100° C. 31.75 9.23  600° C. 22.23 7.68 PASC60 1100° C. 31.75 9.23 1100° C. 34.52 9.73 DAE 1100° C. 43.75 11.03  600° C. 19.36 12.34 DAE 1100° C. 43.75 11.03 1100° C. 34.73 11.79

Embodiment 10 (1) Manufacture of Sample

(a) Compacting Process

PASC60 powder used as the sintered alloy for the automotive structure, which is an alloy powder of iron and phosphorous from Hoganas Co., and DAE powders are compacted in a tensile specimen shape to have density of 6.8 g/cm³ by being pressed by means of the press of 200 ton. The remaining processes are the same as the embodiment 1.

(b) Process of Generating Carbon Nanotube

After dipping the manufactured sintered and finished product into diluted HF solution, natal, diluted sulfuric acid or phosphoric acid, ammonia at a proper temperature is injected and then acetylene, methane gas, or carbonic acid gas is injected to generate the carbon nanotubes in the metal powder particles adjacent to the pores of the molded product.

(c) Sintering Process

The manufactured specimen is sintered for one hour at a temperature of 600° C.

The sintering atmosphere is performed under nitrogen atmosphere and a Mesh Belt sintering furnace is used.

(3) Microstructure Analysis by Scanning Electron Microscope (SEM)

The specimens manufactured by the above process examine the growth shapes of the carbon nanotubes generated in the compacted product and sintered at a sintering temperature of 600° C. by means of the scanning electron microscope (SEM).

FIG. 30 is a scanning electron microscope photograph (20000 magnifications and 50000 magnifications) of specimen sintering specimen generating carbon nanotubes in PASC60 powder molded product at a sintering temperature of 600° C., which is obtained from an embodiment 9 of the present invention; and FIG. 31 is a scanning electron microscope photograph (a: 5000 magnifications and 25000 magnifications) of specimen sintering specimen generating carbon nanotubes in DAE powder molded product at a sintering temperature of 600° C.

As shown in FIGS. 30 and 31, it can be found that the carbon nanotubes are generated in the metal powder particles adjacent to the pores of the compacted product in a net shape. However, it can be found that the carbon nanotubes generated differently from the specimens which are mixed with the carbon nanotubes and sintered cannot be grown into a large carbon nanotube shape even at a sintering temperature of 600° C.

Embodiment 11 (1) Manufacture of Sample

(a) Compacting Process (the Same as the Embodiment 10)

(d) Process of Generating Carbon Nanotube in Compacted Product (the Same as Embodiment 10)

(c) Sintering Process

The manufactured specimen is sintered for one hour at a temperature of 1100° C.

The sintering atmosphere is performed under nitrogen atmosphere and a Mesh Belt sintering furnace is used.

(2) Mechanical Property Measurement by Tensile Test (the Measurement Method is The Same as the Embodiment 1)

The tensile test results are indicated in the following table 10.

As in the Table 10, since the carbon nanotubes are generated in the metal powder particles adjacent to the pores of the sintered product, it is expected that the mechanical strength is more poor than the specimen generating the carbon nanotubes in the metal powder particles, but it can be found that the tensile strength is increased as compared to the specimen of the embodiment 1 made by mixing and combining the carbon nanotubes of 0.1% similarly to the Table 6. It can be found that in order to increase the mechanical strength of composite sintering metal materials, the amount of carbon nanotubes mixed or generated should be increased.

TABLE 10 <The tensile strength measurement results after performing the sintering at 1100° C.> Tensile strength (kgf/mm2) Powder name Results of Results of Results of Powder name embodiment 1 embodiment 6 embodiment 11 PASC60 27.63 39.40 32.05 DAE 22.81 — 27.81

Embodiment 12 (1) Manufacture of Sample

(a) Compacting Process (the Same as the Embodiment 10)

(b) Process of Generating Carbon Nanotube in Compacted Product (the Same as the Embodiment 10)

(c) Sintering Process (the Same as the Embodiment 10)

(d) Process of Additionally Generating Carbon Nanotube (the Same as the Embodiment 10)

(e) Resintering Process

The manufactured toughness adding finished product is resintered for one hour at a temperature of 600° C. and 1100° C.

The sintering atmosphere is performed under nitrogen atmosphere and as a sintering furnace a Mesh Belt sintering furnace is used.

(2) Mechanical Property Measurement by Tensile Test (the Measuring Method is the Same as the Embodiment 1)

The tensile test results are indicated in the following Table 11.

As in the Table 11, it can be found that the tensile strength of the specimens additionally generating carbon nanotubes after impregnating and sintering the carbon nanotubes in the compacted product and then generating the carbon nanotubes in a compacted product are higher as compared to that of the specimens generating the carbon nanotubes after impregnating and sintering the carbon nanotubes in the compacted product, but their elongation is almost the same. It can be found that the brittleness, which is a weak point of the sintered product, can be improved by forming the carbon nanotubes in the pores of the compacted product.

TABLE 11 <The tensile strength and elongation measurement results after resintering> Results of embodiment 9 Results of embodiment 12 Tensile Tensile Powder Sintering strength Elongation strength Elongation name temperature (kgf/mm 2) (%) (kgf/mm 2) (%) PASC60  600° C. 22.23 7.68 35.25 12.07 1100° C. 34.52 9.73 42.19 12.10 DAE  600° C. 19.36 12.34 37.40 14.00 1100° C. 34.73 11.79 54.78 13.20

Embodiment 13 (1) Manufacture of Sample

(a) Mixing Process

PASC60 powder used as the sintered alloy for the automotive structure, which is an alloy powder of iron and phosphorous from Hoganas Co., and DAE powders are mixed with diluted HF solution, natal, diluted sulfuric acid or phosphoric acid using a spraying non-gravity mixer. The commercialized PASC60 powder uses a particle with a powder size of 50 μm to 250 μm.

(b) Compacting Process

The mixed PASC60 powder is compacted in a tensile specimen shape to have density of 6.8 g/cm³ by being pressed by means of the press of 200 ton.

The density measuring method measures density after performing a sintering process according to KS D 0033 (method for determination of density of metal powder sintered materials).

(c) Process of Generating Carbon Nanotube in Compacted Product

The carbon nanotubes are generated by injecting ammonia while applying heat at a proper temperature and then injecting acetylene, methane gas, or carbonic acid gas.

(d) Sintering Process (the Same as the Embodiment 12)

(e) Process of Generating Carbon Nanotube (Toughness Adding Process)(the Same as the embodiment 10)

(f) Resintering Process (the Same as the Embodiment 12)

(2) Mechanical Physical Property Measurement by Tensile Test (the Measuring Method is the Same as the Embodiment 1)

The tensile test results are indicated in the following Table 12.

As in the Table 12, the mechanical strength of the specimens generating carbon nanotubes by being chemically processed in a mixing step is higher as compared to that of the specimens generating carbon nanotubes by being molded and then chemically processed. It is judged that it is more advantageous for generating the carbon nanotubes when gas of carbon group generating the carbon nanotubes are chemically processed in a metal powder particle state.

TABLE 12 <The tensile strength and elongation measurement results after resintering> Results of embodiment 12 Results of embodiment 13 Tensile Tensile Powder Sintering strength Elongation strength Elongation name temperature (kgf/mm 2) (%) (kgf/mm 2) (%) PASC60  600° C. 35.25 12.07 37.85 10.46 1100° C. 42.19 12.10 44.54 10.69 DAE  600° C. 37.40 14.00 39.42 12.25 1100° C. 54.78 13.20 56.59 11.68

Embodiment 14 (1) Manufacture of Sample

(a) Compacting Process

PASC60 powder used as the sintered alloy for the automotive structure, which is an alloy powder of iron and phosphorous from Hoganas Co., and DAE powders are compacted in a tensile specimen shape to have density of 6.8 g/cm³ by being pressed by means of the press of 200 ton.

The density measuring method measures density after performing a sintering process according to KS D 0033 (method for determination of density of metal powder sintered materials).

(b) Sintering Process

The manufactured specimen is sintered for one hour at a temperature of 1100° C.

The sintering atmosphere is performed under nitrogen atmosphere and a Mesh Belt sintering furnace is used.

(c) Process of Impregnating and Combining Carbon Nanotube in Sintered Product

In a manufactured sintered product, organic solution where carbon nanotubes are dispersed is impregnated in the pores of the sintered product by using a vacuum impregnating machine and is heated at a proper temperature so that the carbon nanotubes are combined in the metal powder particles adjacent to the pores of the molded product.

(d) Resintering Process

The manufactured sintered product in which the carbon nanotubes are impregnated and combined is resintered for one hour at a temperature of 1100° C.

The sintering atmosphere is performed under nitrogen atmosphere and a Mesh Belt sintering furnace is used.

(2) Mechanical Physical Property Measurement by Tensile Test (the Measurement Method is the Same as the Embodiment 1)

The tensile test results are indicated in the following Table 13.

As in the Table 13, it can be found that the mechanical strength of the specimens mixing and sintering the carbon nanotubes in the metal powder particles, and then resintering them is higher as compared to that of the specimens resintering the specimens impregnating the carbon nanotubes in the sintered product. Also, the specimens resintering the specimens impregnating the carbon nanotubes in the sintered product has little elongation. It can be found that although the carbon nanotubes impregnated in the sintered product are impregnated and combined in the pores in the sintered product, the tube shape thereof is broken when they are sintered at a temperature of 1100° C., having no effects to increase the elongation.

TABLE 13 <The tensile strength and elongation measurement results after resintering> Results of embodiment 3 Results of embodiment 14 Tensile Tensile Powder Resintering strength Elongation strength Elongation name temperature (kgf/mm 2) (%) (kgf/mm 2) (%) PASC60 1100° C. 31.75 9.23 29.76 Less than 1% DAE 1100° C. 43.75 11.03 32.75 Less than 1%

Embodiment 15 (1) Manufacture of Sample

(a) Compacting Process

PASC60 powder used as the sintered alloy for the automotive structure, which is an alloy powder of iron and phosphorous from Hoganas Co., and DAE powders are compacted in a tensile specimen shape to have density of 6.8 g/cm³ by being pressed by means of the press of 200 ton. The remaining processes are the same as the embodiment 1.

(b) Sintering Process

The manufactured specimen is sintered for one hour at a temperature of 1100° C.

The sintering atmosphere is performed under nitrogen atmosphere and as a sintering furnace a Mesh Belt sintering furnace is used.

(c) Process of Generating Carbon Nanotube in Sintered Product

(2) Microstructure Analysis by Scanning Electron Microscope (SEM)

In the specimens manufactured by the process, the shape of the carbon nanotubes generated in the sintered product is examined by the scanning electron microscope (SEM).

FIG. 32 is a scanning electron microscope photograph (5000 magnifications and 25000 magnifications) of PASC60 powder sintered product generated with carbon nanotubes, which is obtained from the embodiment 15 of the present invention, and FIG. 33 is a scanning electron microscope photograph (a: 5000 magnifications/b: 20000 magnifications) of DAE powder sintered product in which carbon nanotubes are generated.

It can be found from FIGS. 32 and 33 that the carbon nanotubes are generated in the metal powder particles adjacent to the pores of the sintered product in a net shape, making it possible to add the toughness to the sintered product with strong brittleness.

(3) Mechanical Property Measurement by Tensile Test (the Measuring Method is the Same as the Embodiment 1)

The tensile test results are indicated in the following table 14.

As in the Table 14, since the carbon nanotubes are generated in the metal powder particles adjacent to the pores of the sintered product, it is expected that the mechanical strength is poor, but it can be found that the tensile strength is increased as compared to the specimen of the embodiment 2 made by mixing and combining the carbon nanotubes of 0.1% similarly to the table 6. It is judged that it is difficult to quantitatively measure the amount of the carbon nanotubes generated in the metal powder particles, but the larger amount of the carbon nanotubes is generated than the case where the carbon nanotubes of 0.1% is mixed. However, the slightly less elongation is indicated

TABLE 14 <The tensile strength and elongation measurement results after adding toughness> Results of embodiment 2 Results of embodiment 15 Tensile Tensile Powder Sintering strength Elongation strength Elongation name temperature (kgf/mm 2) (%) (kgf/mm 2) (%) PASC60 1100° C. 25.99 8.96 34.05 5.28 DAE 1100° C. 25.64 10.84 34.60 8.44

Embodiment 16 (1) Manufacture of Sample

(a) Compacting Process (the Same as the Embodiment 15)

(b) Sintering Process (the Same as the Embodiment 15)

(c) Process of Generating Carbon Nanotube in Sintered Product (the Same as the Embodiment 15)

(b) Resintering Process

The manufactured toughness added finished product is resintered for one hour at a temperature of 600° C. to 1100° C.

The sintering atmosphere is performed under nitrogen atmosphere and as a sintering furnace a Mesh Belt sintering furnace is used.

(2) Mechanical Property Measurement by Tensile Test (the Measurement Method is The Same as the Embodiment 1)

The tensile test results are indicated in the following table 15.

As in the table 15, the tensile strength is largely increased by generating the carbon nanotubes in the pores of the sintered product and then resintering and alloying them. It can be found that the mechanical physical property values can be increased by repeatedly performing the sintering process and the generating process of the carbon nanotubes.

TABLE 15 <The tensile strength and elongation measurement results> Results of embodiment 15 Results of embodiment 16 Tensile Tensile Powder Sintering strength Elongation Resintering strength Elongation name temperature (kgf/mm 2) (%) temperature (kgf/mm 2) (%) PASC60 1100° C. 34.05 5.28  600° C. 37.13 11.10 1100° C. 39.47 10.23 DAE 1100° C. 34.60 8.44  600° C. 43.07 13.27 1100° C. 58.70 13.73

Embodiment 17 (1) Manufacture of Sample

(a) Manufacture of Tensile Specimen

The sintered finished product is manufactured as SMF 4040M material, which is the sintered alloy for the automotive structure.

(b) Process of Generating Carbon Nanotube in Sintered Product (the Same as the Embodiment 15)

(c) Resintering Process

The manufactured toughness added finished product is resintered for one hour at a temperature of 1100° C.

The sintering atmosphere is performed under nitrogen atmosphere and as a sintering furnace a Mesh Belt sintering furnace is used.

(2) Mechanical Property Measurement by Tensile Test (the Measurement Method is the Same as the Embodiment 1)

The tensile test results are indicated in the following table 16.

As in the table 16, it can be found that the mechanical characteristics of the existing sintered product can be strengthened by generating the carbon nanotubes in the pores of the existing sintered product or impregnating and combining the carbon nanotubes therein and then repeatedly performing the sintering process and the generating process of the carbon nanotubes or the impregnating and combining processes of the carbon nanotubes.

TABLE 16 <The tensile strength and elongation measurement results> Tensile strength (kgf/mm2) Only carbon nanotube Only carbon nanotube Resintered Existing Sintered product sintered Material name Sintered product generated procuct SMF4040M 42.29 52.05 63.64 4.29 52.05 63.64 (Elongation: (Elongation: (Elongation: 1.2% or more) 5% level) 10% level)

As described above, the composite sintering materials using the carbon nanotubes of the present invention is completed by uniformly combining the carbon nanotubes in the metal powder particles or generating the carbon nanotubes therein and growing, alloying, and sintering them or by impregnating and combining the carbon nanotubes in the compacted product or the sintered product or generating the carbon nanotubes in the pores in the compacted product or the sintered product and growing, alloying, and sintering them so that they can be used as the material of the automotive parts, etc.

INDUSTRIAL APPLICABILITY

As described above, the composite sintering materials and a manufacturing method thereof have excellent mechanical, thermal, and electric and electronic characteristics as well as have effects of lowered sintering temperature and material cost reduction so that they are useful as materials for automotive parts, electric and electronic parts, space and aircraft parts, and molding and cutting tools. 

1. A manufacturing method of composite sintering materials using carbon nanotube comprising the steps of: manufacturing master alloys by combining carbon nanotubes with metal powders; growing or alloying the carbon nanotubes by compacting and then sintering the master alloy; generating the carbon nanotubes (including carbide nano particles) in the pores of a sintered product or impregnating and combining the carbon nanotubes therein; and strengthening mechanical characteristics by repeatedly performing the sintering process and the generating process of the carbon nanotubes in the sintered product or the impregnating and combining processes of the carbon nanotubes.
 2. A manufacturing method of composite sintering materials using carbon nanotube comprising the steps of: generating carbon nanotubes (including carbide nano particles) in metal powders; growing or alloying the carbon nanotubes by compacting and then sintering the metal powders in which the carbon nanotubes are generated; generating the carbon nanotubes in the pores of a sintered product or impregnating and combining the carbon nanotubes therein; and strengthening mechanical characteristics by repeatedly performing the sintering process and the generating process of the carbon nanotubes in the sintered product or the impregnating and combining processes of the carbon nanotubes.
 3. A manufacturing method of composite sintering materials using carbon nanotube comprising the steps of: generating carbon nanotubes (including carbide nano particles) in the pores of a compacted product after compacting metal powders or impregnating the carbon nanotubes therein to combine the metal powders with the carbon nanotubes in the pores of the compacted product; growing or alloying the carbon nanotubes by sintering the compacted product in which the carbon nanotubes are generated or with which the carbon nanotubes are combined; generating the carbon nanotubes in the pores of a sintered product or impregnating and combining the carbon nanotubes therein; and strengthening mechanical characteristics by repeatedly performing the sintering process and the generating process of the carbon nanotubes in the sintered product or the impregnating and combining processes of the carbon nanotubes.
 4. A manufacturing method of composite sintering materials using carbon nanotube comprising the steps of: generating carbon nanotubes (including carbide nano particles) in the pores of a finished product sintered after compacting metal powders or impregnating the carbon nanotubes therein to combine the metal powders with the carbon nanotubes in the pores of a sintered product; growing or alloying the carbon nanotubes by resintering the sintered product in which the carbon nanotubes are generated or with which the carbon nanotubes are combined; generating the carbon nanotubes in the pores of the sintered product or impregnating and combining the carbon nanotubes therein; and strengthening mechanical characteristics by repeatedly performing the sintering process and the generating process of the carbon nanotubes in the sintered product or the impregnating and combining processes of the carbon nanotubes.
 5. A manufacturing method of composite sintering materials using carbon nanotube comprising the steps of: manufacturing master alloys by combining carbon nanotubes (including carbide nano particles) with metal powders or generating the carbon nanotubes in metal powders; mixing the master alloy or the metal powders, wherein the carbon nanotubes are generated, with another metal powders or ceramic materials; growing or alloying the carbon nanotubes by compacting and then sintering the mixture; impregnating and combining the carbon nanotubes in the pores of a sintered product or generating the carbon nanotubes therein; and strengthening mechanical characteristics by repeatedly performing the sintering process and the generating process of the carbon nanotubes in the sintered product or the impregnating and combining processes of the carbon nanotubes.
 6. A manufacturing method of composite sintering materials using carbon nanotube comprising the steps of: mixing metal powders with ceramic materials; compacting the mixture or compacting and then sintering it; generating and impregnating the carbon nanotubes (including carbide nano particles) in the pores of a compacted product or a sintered product or combing the carbon nanotubes therein; growing or alloying the carbon nanotubes by sintering the compacted product; and, strengthening mechanical characteristics by repeatedly performing the sintering process and the generating process of the carbon nanotubes in the sintered product or the impregnating and combining processes of the carbon nanotubes.
 7. The method of claim 1, wherein the metal powder particles combining the carbon nanotubes or generating the carbon nanotubes (including carbide nano particles) are Fe, Ni, Co, W, and Si powders or are alloy powders in which Fe, Ni, Co, W, and Si are alloyed.
 8. The method of claim 1, wherein the matrix ingredients of the compacted product and the matrix ingredients of the sintered product impregnating the carbon nanotubes or generating the carbon nanotubes (including carbide nano particles) are Fe, Ni, Co, W, and Si and are alloy powders in which Fe, Ni, Co, W, and Si are alloyed.
 9. Composite sintering materials obtained by a manufacturing method of claim
 1. 10. A manufacturing method of composite polymer materials using carbon nanotube comprising the steps of: manufacturing master alloys by combining carbon nanotubes and metal powders or generating the carbon nanotubes (including carbide nano particles) in the metal powders; mixing the master alloy or the metal powders wherein the carbon nanotubes are generated, with polymer materials; growing the carbon nanotubes by melting the mixture by a heater; injection-molding the mixed melting material; and aging the injection-molded product.
 11. The method of claim 10, wherein the metal powder particles combining the carbon nanotubes or generating the carbon nanotubes (including carbide nano particles) are Fe, Ni, Co, W, and Si powders or are alloy powders in which Fe, Ni, Co, W, and Si are alloyed.
 12. Composite polymer materials obtained by the manufacturing method of claim
 10. 13. The method of claim 2, wherein the metal powder particles combining the carbon nanotubes or generating the carbon nanotubes (including carbide nano particles) are Fe, Ni, Co, W, and Si powders or are alloy powders in which Fe, Ni, Co, W, and Si are alloyed.
 14. The method of claim 3, wherein the metal powder particles combining the carbon nanotubes or generating the carbon nanotubes (including carbide nano particles) are Fe, Ni, Co, W, and Si powders or are alloy powders in which Fe, Ni, Co, W, and Si are alloyed.
 15. The method of claim 4, wherein the metal powder particles combining the carbon nanotubes or generating the carbon nanotubes (including carbide nano particles) are Fe, Ni, Co, W, and Si powders or are alloy powders in which Fe, Ni, Co, W, and Si are alloyed.
 16. The method of claim 5, wherein the metal powder particles combining the carbon nanotubes or generating the carbon nanotubes (including carbide nano particles) are Fe, Ni, Co, W, and Si powders or are alloy powders in which Fe, Ni, Co, W, and Si are alloyed.
 17. The method of claim 6, wherein the metal powder particles combining the carbon nanotubes or generating the carbon nanotubes (including carbide nano particles) are Fe, Ni, Co, W, and Si powders or are alloy powders in which Fe, Ni, Co, W, and Si are alloyed. 